Generally, in a magnetic resonance imaging apparatus (hereinafter, also referred to as an MRI apparatus), a resonance frequency of water, which is a collection target of signals, is set to a center frequency of radio frequency pulses when performing a pulse sequence. For this reason, a frequency spectrum is collected by performing a fat suppression pulse sequence in a pre-scan performed prior to a main scan by which a diagnostic image is collected, and the resonance frequency of water is identified by analyzing the frequency spectrum.
In an example of such conventional MRI apparatus, the frequency spectrum is collected by performing a pulse sequence with a short time inversion recovery (STIR) technique in the pre-scan and identifies a maximum peak of the frequency spectrum as the resonance frequency of water. In another example of the conventional MRI apparatus, the frequency spectrum is displayed on a display thereof, and a user visually selects a peak of the frequency spectrum displayed on the display and identifies the resonance frequency of water. It is difficult to identify the resonance frequency of water in some cases, such as a case where a maximum peak is not always the resonance frequency of water, and another case where a plurality of peaks are present as candidates, and still another case where disturbance occurs in a spectrum waveform due to a high fat content. In the STIR technique, a signal is collected at timing of an inversion time when longitudinal magnetization of fat reaches its null point by utilizing a difference in longitudinal relaxation time between substances.